a multicentre general practice study was undertaken to compare the efficacy of two proprietary dithranol preparations, Psoradrate 0.1% and Dithrocream 0.1%, in the treatment of chronic psoriasis, using a single blind, within-patient trial design. A total of forty-nine patients entered the study and treatment lasted for 6 weeks. Psoradrate 0.1% produced a greater mean per cent clinical improvement in psoriasis than Dithrocream 0.1% at each stage of the trial, and this difference was statistically significant (p equal to 0.025) at 4 weeks. The evidence also suggested that Psoradrate 0.1% resulted in greater reductions in psoriatic scaling. most patients found that the Psoradrate 0.1% was more effective and a significant majority (p equal to 0.01) thought that it worked faster than Dithrocream 0.1%. Although the increased effectiveness of the Psoradrate 0.1% was associated with a higher incidence of stinging/burning of the skin, this was not reflected in the patients' overall opinions of the treatments. Twenty-three patients preferred Psoradrate as against seventeen who preferred Dithrocream.